The present invention relates to a method of producing aluminum alloy heat-exchanger. In more detail, it relates to a method of improving the thermal efficiency, strength and corrosion resistance of heat-exchanger produced by soldering technique.
The heat-exchangers such as radiator used for cars etc. have a structure, wherein, for example, as shown in FIG. 1, thin-wall fins (2) machined into corrugated shape are formed unitedly between a plurality of flat tubes (1) and both ends of these flat tubes (1) are opened respectively toward spaces constituted with header (3) arid tank (4). A high-temperature refrigerant is fed from the space on the side of one tank to the space on the side of other tank (4) through the flat tubes (1) and the refrigerant having become low temperature through the heat-exchange at the portions of tube (1) and fin (2) is circulated again to the external portion.
The materials of the tube and header of such heat-exchanger the, for example, a brazing sheet wherein JIS 3003 (Al-0.15 wt. % Cu-1.1 wt. % Mn) alloy is used as a core material and, on one side of said core material, JIS 7072 (Al-1 wt. % Zn) alloy is cladded as an internal lining material and, on the other side, JIS 4045 (Al-10 wt. % Si) alloy or the like is cladded usually as a soldering material is as the side of said internal lining material which becomes inside, meaning, the side which contacts the refrigerant at all times. Moreover, for the fin material, corrugated JIS 3003 alloy or an improved material allowed to contain Zn etc. for the purpose of giving the sacrificial effect thereto is used.
And, these are assembled unitedly by soldering.
Next, in the prior art multilayer type evaporator, as shown in FIG. 2, fins (5) and pathway-constituting sheets (6) and (6') forming path way (7) of refrigerant and comprising brazing sheet are layered alternately and these are joined by soldering. For this fin (5), around 0.1 mm thick brazing sheet is used ordinarily and, for the pathway-constituting sheet (6) or (6'), about 0.5 mm thick brazing sheet is used.
For such evaporator, for preventing the pathway of refrigerant from the external corrosion, a fin material comprising JIS 3003 alloy or an alloy allowed to contain Zn etc. for the purpose of giving the sacrificial effect thereto is used and, for the material of refrigerant's pathway, an alloy added with Cu, Zr, etc. to Al-1 wt. % Mn alloy, if necessary, is used as a core material and, on the surface, soldering material such as JIS 4004 (Al-9.7 wt. % Si-1.5 wt. % Mg) alloy or JIS 4343 Al-7.5 wt. % Si) alloy is cladded and used.
The prior art serpentine type condenser is shown in FIG. 3. In this, a tube (8) molded by extruding tubularly in a hot or warm state is folded meanderingly and, in the openings of this tube (8), corrugated fins (9) comprising brazing sheet are attached. Additionally numeral (10) in the diagram indicates a connector.
As the materials of such condenser, for said tube, JIS 3003 alloy or the like is used and, for the corrugated fin, such one that JIS 3003 alloy or an alloy allowed to contain Zn etc. for the purpose of giving the sacrificial effect thereto is used as a core material and, on both sides, soldering material such as JIS 4004 alloy or JIS 4343 alloy is cladded is used.
All of above-mentioned heat-exchangers etc. are assembled by brazing to unify by heating to a temperature near 600.degree. C. and joining with soldering material. This brazing method includes vacuum brazing method, flux brazing method, a brazing method using a potassium fluo-aluminate brazing flux (NOCOLOCK) which is non-corrosive, and the like.
The trend in heat-exchangers is toward lighter weight and miniaturization and, for this reason, thinning of wall of materials is desired. However, if thinning of the wall is made with conventional materials, then first there has been a problem that, as the thickness of materials decreases, the thermal conductivity ends up to decrease resulting in decreased thermal efficiency of heat-exchanger. For this problem, Al-Zr alloy material etc. have been developed as conventional fin materials, which, in turn, have a new problem of low strength.
Moreover, as a second problem, there is lack of strength by thinning the wall. For this problem, some high-strength alloys have been proposed, but any alloy with sufficient strength is still not obtained. This is because the ingredients of high-strength alloys themselves are restricted in view of the solderability, corrosion resistance, etc. aforementioned and, in addition, due to the brazing to be heated near 600.degree. C. in the final process of production, strength-improving mechanisms such as hardening cannot be utilized.
As a result of extensive investigations in view or this situation, a production method of aluminum alloy heat-exchanger with excellent thermal efficiency, high-strength and excellent corrosion resistance has been developed by the invention.